Some weather averages

The catalyst for this post began with a view that it is much windier at Mallacoota this year than we have noticed in the past.  I then discovered a table of monthly averages including 9am windspeed.

Comparing the values for 2019 to date with the previous averages for Mallacoota shows that in fact this year is a little below past averages!

So I wondered whether the difference was due to comparison with Canberra.  An initial issue was that the current Canberra Airport data doesn't include the average windspeeds which I find astonishing - surely that would be a crucial measure for an airport.  However, nothing that Canberra Airport does - that might save them a few bucks - should surprise anyone.  Fortunately the data is available for the Airport Comparison site although it closed in 2010.  Yes, Mallacoota is windier!

While browsing the daily observations for Victoria on 9 April I noticed in passing that Wilson's Promontory had recorded a gust of 102kph.  Yowza!  So I looked up the average wind speeds for that location: for both 0900 and 1500 it is pretty much a steady 30kph through the year!  That is about double Mallacoota!

My second lot of averages are daily average temperatures for April.  I have calculated these from the BoM data on Maximum and Minimum temperatures for Mallacoota.  The catalyst for this was observing that for March the average mean temperatures hardly moved across the month.  Did the same apply to April?

No siree!  Whether one looks at the average for each day or the cumulative (ie month to date) series there is a pretty fair drop across the month,  Obviously, the cumulation process smooths the series out so has a higher correlation coefficient.

I have added in the daily values for 2019 which shows a pretty consistent high average.  That may be about to change, but thus far the difference between current mean temperature up to 7 April is 1.7C above the long term average.

Lower Lake and Double Creek

On April 1 we visited Captain Stevenson's Point to see what birds could be seen.  The first sight was a vigorous surf outside the outlet.

 The sandbars around the Lower Lake are back in force.

 Before I set up my telescope to check the birds Frances spotted a large stingray swimming in the shallows.  My attempts to photograph it were not good. However it was in shallow water so that the wings came out of the water as it swam,

Based on large size and distribution I originally thought it was a Smooth Stingray. However Frances then found information about Eagle Rays, which lift their wingtips out of the water when in the shallows. Checking the image in Fishes in Australia http://fishesofaustralia.net.au/home/species/3545 that matches very well. So, Southern Eagle Ray Myiobatis tenuicaudatus it is.

Looking across to the West of the opening there was a pretty good group of small waders: at least 8 Double-banded Plovers; about 4 Red-capped Plovers (almost certainly more that I didn't see) and at least 35 Red-necked Stints. Also 14 Pied Oystercatchers; 5 White-faced Herons; and offshore a good number of Gannets and a high flying Sea Eagle.

Just off the Point a Crested Tern was making splashing noises as it dived for fish.  It then dripped as it emerged from the water.

 On 2 April I decided to explore the Double Creek Arm.  A friend, who visited before the Inlet was opened, had advised of meeting signs at Double Creek talking of the track being flooded.  The signs were still there!

 And so indeed was the flood.

So back to the road and try the Charlies Creek track on the other side of Double Creek.  Same, same!

 I did get a bit further in before hitting that lot of water and had passed this interesting looking expanse.   I shall try it again when the water has had a bit longer to drain away.

Draft March 2019 Weather report

I have called this a draft weather report as I have had a small computing disaster which means that I don't have access to a bunch of data I had previously compiled.  I hope this will be recovered in the nearish future at which point some of the material which follows may be augmented.  However, what's here should give some idea of what went on, and how it fits into history.

The material relating to the current month will, unless otherwise stated, be based on readings from my weather station (a Davis Vantage Vue on Angophora Drive, Mallacoota).  As that has only been functional for 6 weeks material comparing this month with longer term data will largely be based upon BoM data for Mallacoota, collected from a site near the Airport.

Overall Summary

The month was basically quite warm, with both average maximum and average minimum above the long term averages for the month.  

With a few very damp days rainfall is also above average, bringing the rainfall year to end of March (195 mm) close to the long term average (200 mm).

There were a few pretty windy days.  However the BoM average maximum daily gust came in at 40.0 kph compared with ~41 kph for March 2018 (as assessed by eyeballing a graph in the report for February 2019) - so probably about normal.

For relative humidity the 0900 hrs rH for this year was a little higher than last year (also from eyeballing a graph) while the 1500 hrs value at 69% was much higher than last year.  This probably reflects the rather low rainfall of last year.  A separate page on the BoM site confirms the average value for 0900 hrs close to 70% and shows the average 1500 hrs rH  is 66% - so again very close to normal.  The humidity data for my site is very similar to the BoM material.

On to the details.

Rainfall

As noted above the rainfall - as reported at the BoM site - was above the long term average.  It was also greatly above last year's miserable effort!  It brings the year-t-date value to within 5mm of the average fall to end March

The mean annual rainfall, since 1985,  at the BoM site is 935 mm.  Doing a pro-rata extrapolation of this suggests the total fall for 2019 will be close to 910mm  

Rain at home was about 13 mm greater than at the BoM site.  This can be expected when the falls are mainly due to thunderstorms.  It is a tad difficult to reconcile the two series as BoM (for reasons of historical consistency) use days ending at 0900 whereas I (for reasons of ease of compilation and common sense) use a day ending at 2400.  That being said here are the daily falls.

Temperatures

An overall comment on temperatures is that the monthly mean temperatures compare well between my site and the BoM site.

Generally the daily values are similar (within 3%) except where a cool change comes through early in the day.  That allows my maximum temperature for the day to be recorded early in the morning which may be well in excess of the BoM maximum recorded after 0900.  As the correlation coefficient is 0.94 the pattern across the month is still quite similar. Restricting my observations to those after 0900 gives a higher correlation coefficient of 0.98.

Maximum temperatures

The first chart compares BoM data on average maximums for this year. last year, and all years since 1995  While the month was above average, it was not as hot as 2018.

Looking at data for my site for 2019  shows a hot start to the month before settling down to a fairly stable middle of the month and a cooler last few days.

I have managed to chart when each day's maximum was recorded.  Usually in the afternoon but the two days with cold fronts stand out rather well!

Minimum Temperatures

Again begin with data for the BoM site.  In this case the minima average out to be well above both average and last year.  

 The daily values show very warm minima early in the month and, after a cool period, later in the month before finishing with some lower temperatures,

Most of the minima are expected between 0400 and 0800 but a few occurred late in the evening, presumably as a cool change arrives.

Average temperatures

Two measures of the mean temperature are available:

• For the BoM series it it the mean of the daily maximum and minimum; 
• For my own series it is possible to take the average of the 24 hourly readings.

As is clear from the graph the pattern between the two series s very consistent (correlation coefficient 0.98).

A main use of the average is to calculate the temperature anomaly which is the difference between the average for the current period and the long term average.  For March this comes to +1.2C, so a bit warmer than average.

Humidity

On comparing the BoM average values for the month with the long term averages given on the BoM site they are very similar.  Most comments are given in the preamble so here is a chart of daily values for home, for the two standard times.

The most surprising feature is that they are relatively close,  For Carwoola, which is much more inland  the 3pm rH is usually much lower.
Wind

I have taken my standard measure of windiness as the maximum daily gust.  BoM do not publish that measure as a long term average.  They do publish the averages for 0900 and 1500 speeds and in both cases the speeds for 2019 were below average.

I have compiled a chart of maximum daily gusts for the month for my system.

The 61kph blast on the 29th was impressive!

I have compiled a wind rosette in which the width of the segments reflects the number of readings from that direction.  There were no readings from the East or South, and the labels are a mess from ESE to SW!

Mammals and fungi

I have no images of the mammals but the sightings have been:

• A Grey-headed Flying-fox dining in a flowering banksia in a neighbour's garden; and 
• An Australian Fur Seal lounging on the suface about 200m off Point Difficult yesterday afternoon.

A friend from a weather forum reckons the wet weather at Katoomba is causing the bioluminescent fungi in that area to be performing well.  I haven't managed to locate any of that in this area yet but there are getting to be a range of fungi about.  The identifications blow are rather tentative - comments welcome.

Leucocoprinus birnbaumii (Angophora Drive)

No ID yet (Point Difficult)

 Macrolepiota clelandii (Mirrabooka Avene, near top entrance to Angophora Drive)

Musings about water levels and rain

In the Community Facebook page a comment has been made that the day after the opening was made the level of the Inlet has risen by 50 mm.

That led me to wonder how that relates to recent rainfall.  In what follows many of the necessary bits of data are not available but I think it sort of hangs together.

My weather station (Angophora Drive) has recorded somewhat over 50mm in the last 7 days.  One could make an assumption that this is about average for the catchment of the Inlet  - and checking against BoM data for Cann River and Cathcart that seems not unreasonable.  There are 3 things that could happen to the rain:

1. Sink into the ground
2. Run off into the the river system; 
3. Evaporate.

Given recent weather I think evaporation is not a major player.  I have no idea of the split between points 1 and 2: on the one hand the soil currently has plenty of capacity (favouring (1)) but on the other hand a significant fall in a short time will favour (2).  For a mind-game, I assume 10% of the rain has run off.

It is going to take a while for the water to get here.  The headwaters of the Genoa are at least 45 kms from the mouth of the Inlet in a straight line and probably double that in river kilometres.  That means it is going to take a while  - probably 3-4 days (??) - for some of the run off water to get here.  As most of the rain was several days ago one could assume that most of it has now got here, probably arriving in the last two days

I have read somewhere today that the surface area of the Inlet is  25 sq km (or 2,500 Ha).  Eyeballing Google Earth and following the course of the Genoa and Wallagaraugh Rivers suggests that the catchment area of the Inlet is about 40 km x 25 km (~80,000 Ha).  For the sake of argument, say I have got that way wrong and it is only 40,000 Ha.  That still means the area of the catchment is 16 times that of the Inlet.  

Bringing these guesses together we have 50mm of rain x 10% run-off x 16 times area (50*0.1*16)= an "expected" rise of 80 mm.

Then bring in the new factor of the opening to the sea.  which is about 10m wide.  I have run out of imagination in trying to assess how much water is flowing out in any given time period, but if it has released close to half the water that has arrived through the Narrows in the last 24 hours I reckon that is both believable and beneficial.

The Inlet now has an outlet.

I recently got an email from a resident of Manila, Philippines to the effect that the Inlet was to be opened on 21 March.  This was going to happen so that it finished at low tide (1330).  We drove down on that day and had finished unpacking the car by 1530, so I took myself off.

So did quite a few other people!

On the way I noted the height of the water relative to the road ...

,,, the fish cleaning station and....

.... the wharf.

I had wondered how they would get earth moving equipment into the area.  The answer is to heap sand over the rocks at Bastion Point!

Excavator tracks - and notice the number of people on the beach.

Gippsland Ports had declared a no=go area near the outlet and sent a boat to monitor it.  I think this tinny driver got the word.

Some images of the channel.

There is obviously a good flow!

There was a lot of sand moved!  I think the Ranger calculated 2000 cubic metres in total (and I'm not sure is that included the ramp at Bastion Point).

The local kids turned up in force!

This was being monitored by a Ranger to ensure nothing dangerous happened.  He explained the role of the various agencies involved:

• The Gippsland Catchment Management Authority look at the theoretical aspects of the opening and decide when it could be done.  This seems a fair summary of the considerations.
• They get Parks Victoria to look after the operation (ie do the work); 
• Gippsland Ports are responsible for the maritime safety (ie keeping boats out of a dangerous area)

Basically all sensible when explained that way.

The next day (22 March) there is a good flow to the oceean

 .. and the water has started to carve its own way into the exit.

The opening is in a good spot as the area the waders are using is still accessible with dry feet.  This is a pair of Red-necked Stints.

Walking back along the beach a couple of very large dark gulls appeared,  (The nearest one is actually smaller and white - or Silver.)

They are Immature Pacific Gulls: note the massive bill.

The beach was well endowed with Bluebottles so shoes are good!

Sunrise and an Egret

After yesterday's continual murk, it was good to see the cloud breaking up at sunrise.

Mid afternoon I was pretty excited to see this bird shown in the following image land in the next-door-but-one paddock. Initially identified as a Cattle Egret,

... but this swiftly revised as this image to Alpaca Egret!

Birding and other stuff

The day started off well with 3 Wedge-tailed Eagles in a cypressy-looking tree near home.  The third ne is a young bird, indicated by a yellow arrow.  It whinged constantly.

A birding friend from Canberra was in town today so we spent the morning visiting a few sites.  The first, Gun-Club Track, was a waste of time: the only bird seen was a Welcome Swalllow.  We did hear a Treecreeper nearby but still pathetic.

We then stopped at Betka Beach where the birds were more obliging, especiallythe Hooded Plovers of which we saw 2.  Hopefully Jnr was nearby somewhere.

On to Bastion Point where we got some good birds despite some funsters walking right through the flock of Gulls and Terns.  Bird of the Day was Red-necked Stint  but there were also good numbers of Red-capped Plover and a large flock of Short-tailed Shearwaters over the ocean.

On to the recycled Water Treatment Plant.  A first sighting there was a Koala in the gum plantation..

The walk in was quite quiet in terms of birds but the ponds soon began to deliver,  Overall numbers were quite good, but not record breaking.  A young Wedgetail - possibly the one seen near home this morning as its only 2.5kms away - posed nicely

As we moved to the big pond my friend spotted what he first thought was a discarded tyre.  Then he realised it was a humungous Red-bellied Black Snake.  We estimated it as at least 2m long and the body as thick as our arm.

It was happily  eating frogs and such like but on dropping a couple of rocks it poked its head up.

Calling in at the small wetland with a hide we saw 2 Spotless Crakes ...

,, and a single Black-fronted Dotterell.

Getting back to the caravan Park and another Koala had been spotted.